Fluke 83V 11amp fuse... interchange ?

[r-mm]

Managed to blow the big fuse in my 83V.  I'm not very familiar with cartridge type fuses.  Is this something I should buy from Fluke or is there a good interchange?

https://www.mouser.com/ProductDetail/Fluke/803293?qs=aZCcseWLxnv0rmDDerivdw%3D%3D&mgh=1

Since I'll probably do something thick in in the not too distant future I wouldn't mind finding a dozen at a better price...

[floobydust]

These fuses are just silly expensive. They are sand-filled, have regulatory approvals, melamine/ceramic body and are special for multimeters. I'd just bite the bullet and replace it.
There are lower cost chinese knockoffs. But because the fuse has a safety function - I wouldn't use them, they're usually missing arc-quenching sand.

More discussion:
https://www.eevblog.com/forum/testgear/fake-bussmann-multimeter-fuses-on-ebay-dmm-b-44100-r-and-dmm-b-11a/
https://www.eevblog.com/forum/testgear/fluke-77-fuse-bussman-ktk-15-counterfeit/msg3211864/#msg3211864

EEVBlog sells multimeter fuse kits

[nightfire]

Basically lots of fuses can be replaced with other (brand) fuses that match their specs.

But: In a Multimeter fuses have to work up to 1000V AND guarantee a certain breaking capacity in a small form factor- thats why they are quite expensive once you leave CAT II territory.
I would have no problems replacing a bussman fuse with their appropriate counterpart from SIBA or so, but there sometimes is a lot more to a fuse as what would catch the eye:

- Size/Dimension
- Breaking capacity (prospective short circuit current that they can safely terminate without having an arc between their poles)
- breaking time/characteristic (which amount of short spikes are tolerated and at which energy passing they begin to melt)
- Working of to a certain voltage, above 500V they get quite expensive
- internal resistance and therefore heat dissipation due to voltage drop whilst measuring high currents

Usually we are talking 20 kA or more breaking capacity in a CAT IV multimeter, and that is in that small form factor not quite easy to ensure. And thats why those fuses are so big in diameter- usually 10x38 mm. With lower energies, a small 6,3x32mm would be quite sufficient and cheaper.

With my last job I have done lots of short-circuit current calculations in a industrial site with a 20kV transformer to check the validity of the fuses and their selectivity against each other, and what the server cabinets would place as a stress in a short-circuit scenario to the UPS systems, and there is sometimes a bit  more to the way a fuse really melts than catches the naked eye. Here the fuse also takes up some energy and limits the short-circut current, therefore also protecting the valuable electronic stuff beneath it.

[bdunham7]

https://witonics.com/collections/bussmann/DMM

If you are working on low-voltage stuff, you can make yourself a set of fused test leads and use a 5 amp fuse.  If you mistakenly plugged it into a wall with the leads on the 10A setting, then be glad you had an expensive fuse to keep the molten meter parts out of your eyeballs.

[nightfire]

Side note: In germany, the short circuit current of a 230V wall outlet (depending on the distance to the street transformer and internal cable length in the house) is usually between 200A and 600A.
(I do those electrical safety checks at work, and those numbers were measured with a special installation tester designed for that task)

[Gyro]

Those figures actually sounds quite low against worst case (compared to my house in the UK anyway). The Ze of the installation, measured at the input of the distribution board is 0.1R (2.45kA at the time of measurement) and is guaranteed to be less than 0.35R by the supply company. That's a fair proportion of the 6kA rating of the RCBOs. Measuring the Zs at one of the sockets on the 32A ring (one fairly close to the distribution board) still reads 0.17R (around 1.4kA at 240V).

It really does go to show that these meter fuse breaking capacity ratings are indeed very important if you're going anywhere near the mains.

[r-mm]

I see your points.  I shorted the meter thru a car battery and am pleased to still have

a)hands
b)a fluke meter

so eight bucks seems a fair price of admission.  maybe next time i'll switch the leads from the amp setting before checking voltage...

[Gyro]

Ah, a car battery. In that case you're only in the territory of 600-800A DC into a short circuit - just enough to light up a spanner.    That's more in the hopping about with burnt fingers, smoking leads and shunt turning to a metal blob territory rather than blowing up in your face. If you were doing the same on a 24V truck the fuse would have a bit more trouble clearing the arc.

so eight bucks seems a fair price of admission.  maybe next time i'll switch the leads from the amp setting before checking voltage...

I've often wondered if an element of the fuse cost is to teach the user to be more careful in future!  Many of us have done it at some time but treating current measurement an exception and ensuring that you immediately return the leads to the voltage sockets afterwards is a good habit to get into.

Yes, $8 is a lot cheaper than a new meter.

[nightfire]

Those figures actually sounds quite low against worst case (compared to my house in the UK anyway). The Ze of the installation, measured at the input of the distribution board is 0.1R (2.45kA at the time of measurement) and is guaranteed to be less than 0.35R by the supply company. That's a fair proportion of the 6kA rating of the RCBOs. Measuring the Zs at one of the sockets on the 32A ring (one fairly close to the distribution board) still reads 0.17R (around 1.4kA at 240V).

It really does go to show that these meter fuse breaking capacity ratings are indeed very important if you're going anywhere near the mains.

When you have a ring, this means you will have double the conductivity of the wires- and maybe a bigger cable cross section- here in germany its usually 1.5 mm² (16AWG), and its only a straight line from distribution cabinet to wall outlet about 20 meters away...
In that case, the numbers will match due to different conductivity...

Also not to forget: IN case of a short, the high-voltage feeder network and transformer themself also have an important role, and sometimes they do not live up to the theoretical possibilities of a low restistance circuit on their secondary side...

Another hint I memorized: I does not matter how powerful a transformer ist- at least 3 Meter of 1.5 mm² (single phase) and the short curcuit current can not exceed roughly 2000 Amps because of the dampening factor of the  wire resistance...

[Gyro]

We do indeed have very different wiring systems (carefully trying not to trigger another UK vs US ring vs radial 'debate' again ).  1.5mm² is thinner than I expected for a socket circuit [Edit: but of course your breaker trip ratings are much lower]. We often use 1.5mm² for lighting circuits here, which is massive overkill these days. Our rings are wired in 2.5mm² which means much lower resistance, particularly as you get back towards the distribution panel (consumer unit).

Our cooked outlets are typically wired in 6mm² (a hangover from the de-rating factor for the old 30A re-wireable fuses) and often include a 13A socket for a kettle etc. The prospective fault current there can be very close to that of the incoming supply. Thank heavens for fused plugs.

[tooki]

Managed to blow the big fuse in my 83V.  I'm not very familiar with cartridge type fuses.  Is this something I should buy from Fluke or is there a good interchange?

https://www.mouser.com/ProductDetail/Fluke/803293?qs=aZCcseWLxnv0rmDDerivdw%3D%3D&mgh=1

Since I'll probably do something thick in in the not too distant future I wouldn't mind finding a dozen at a better price...

Fluke itself just resells the fuses they buy from Bussmann. But honestly, the price via fluke is often the lowest!

There are three manufacturers of fully compliant multimeter fuses for the Fluke 80 series (and many other industrial meters, like my Keysight) that I’m aware of (for the 11A and 440mA, respectively):
Bussmann DMM-B-11A and DMM-44/100-R
Littelfuse FLU011 and FLU.44
SIBA 5019906.11 and 5021006.0,44

I would not hesitate to use any of those. There may be others that make them, but I haven’t come across any others, even after looking extensively. (I work at a vocational training center, and of course beginner apprentices burn out the 440mA fuses far more often that we’d like, so cheaper alternatives would be nice, but have proven elusive.)

Note that the 440mA fuse is 35mm long, while the 11A is 38mm long. The longer one is a common fuse size, the shorter one is much, much rarer, and is used here to prevent insertion of a different fuse type. There are lots of cheaper 38mm fuses in 400mA and 500mA, but they will not fit. (SIBA makes 440mA DMM fuses in both 35 and 38mm long, so be sure to use the part number above to ensure you get the 35mm one!)

Multimeter fuses are designed to interrupt huge fault currents without exploding, but also to blow extra fast. (Faster than standard “fast blow” fuses.) So don’t attempt to replace them with cheaper fuses. What you can do safely when working on non-mains circuits, however, is to use another, smaller-value fuse in series (in your test leads) to blow first For example, if you know your circuit isn’t supposed to draw more than 5 amps, you could use a cheap 5A fuse, so that if 10A of current pass, it’ll blow but the expensive DMM fuse won’t. But don’t expect, for example, a “fast” 10A glass fuse to reliably protect the 11A DMM fuse, since a fault current could blow the 11A fuse first, since it’s faster.